The present invention relates to data processing systems and data processing methods, and particularly relates to systems and methods for processing data for use in digital TV (DTV) broadcasting, digital versatile discs (DVDs) and Blu-ray discs, for example.
In DTV systems, data received by antennas and subjected to preprocessing takes the form of transport streams (TS). The DTV systems are MPEG-2 systems. In MPEG-2, in addition to the transport stream mentioned above, a program stream (PS) and a packetized elementary stream (PES) packet, which is defined as intermediate data in conversion between the transport stream and the program stream, are used as a data sequence. These data streams are processed as an elementary stream (ES) in the end of processing. These streams (i.e., TS, PS, PES and ES) have respectively different formats according to established standards.
In a DTV system, a transport stream subjected to preprocessing is received by a transport decoder (TD) and divided into audiovisual (AV) data such as an audio signal (audio data), a video signal (video data), a teletext signal (teletext data) and section data such as encryption information and program information, and the divided data is transferred to an external memory to be temporarily stored therein. Out of the temporarily stored data, section data is processed by software in a CPU and AV data is recorded in another devise or is transferred from the external memory to an AV decoder in response to calling from the AV decoder to be decoded.
Processing in the TD is specifically disclosed in patent documents as follows. For example, a storage means for a multiplexed data stream is disclosed in Japanese Unexamined Patent Publication No. 9-275381. A system LSI in which a TD, an AV decoder and a CPU are integrated on one chip is also known. In such a system LSI, memories in which data is temporarily stored are externally provided to the TD and the AV decoder, respectively (see, Japanese Unexamined Patent Publication No. 2001-69106, FIG. 1). As detailed processing in an AV decoder, scaling on video signals in horizontal and vertical directions is disclosed in Japanese Unexamined Patent Publication No. 11-355683.
On the other hand, AV data used in, for example, data for DTV, DVDs and blu-ray discs (BDs) is not permitted to be transferred to transmission lines such as peripheral component interconnect (PCI) buses, Ethernet (a registered trademark) and universal serial buses (USBs) in decrypted states, so that encryption and decryption are needed to perform AV data processing such as recording and dubbing. For encryption and decryption, a buffer having a large capacity is necessary, so that many of systems for encryption and decryption are provided with external memories (see Japanese Unexamined Patent Publication No. 7-297855).
With the foregoing conventional techniques, AV data input to a system LSI from an external device such as a hard disk drive (HDD) is recorded on a recording medium in the following manner. The input data is stored in an external memory externally provided to the system and then is decrypted. The decrypted data is stored in the external memory again and then is encrypted. The encrypted data is transferred to the recording medium.
In such processing, a large part of the band width (transmission band) of the external memory is used and CPU processing is increased for control of the external memory. On the other hand, in a large-scale LSI, external memories are unified to suppress the cost, so that a plurality of interfaces perform data transfer to/from one memory interface. Accordingly, the recording speed on an HDD or other media largely depends on the band width of an external memory and adversely affects the performance of a CPU.